Sleep apnea is a condition that occurs when a person regularly stops breathing for ten seconds or longer during sleep. It is a form of sleep-disordered breathing. The severity of sleep apnea can be classified according to the number of times per hour a person stops breathing (apnea) or has slowed breathing (hyperpnoea). Apnea episodes can happen from five to fifty times an hour.
During an apnea episode, a person's blood oxygen level may drop. Over time, low blood oxygen levels can lead to serious health problems and early death. People who have sleep apnea may be at increased risk for developing high blood pressure (hypertension), high blood pressure in the lungs (pulmonary hypertension), depression, mental impairment, irregular heart rhythms, heart disease, and stroke. They also may have a higher-than-average rate of automobile and work-related accidents.
Sleep apnea usually is caused by a blockage (obstruction) in the nose or mouth. A blockage may be caused by defects in the nose or enlarged tissues in the nose, mouth or throat. About 2-4% of people suffer from sleep apnea and affects all age groups. People who have sleep apnea often (but not always) snore loudly and tend to be sleepy throughout the day. Common symptoms include: tossing and turning during sleep and feeling as through they are suffocating; complaining that they are tired all fo the time; awakening with morning headaches and feeling irritable and not rested; failing asleep at inappropriate times, such as while eating, driving or talking; and having problems doing their jobs. The bed partner of a person with sleep apnea may notice periods when the person stops breathing while sleeping.
A sleep study (polysomnography) is the only way to positively diagnose sleep apnea. For some people who have sleep apnea, losing weight, developing good sleeping habits and avoiding alcohol and sleep medications may cure the condition. However, other people may need to use a breathing device that provides continuous positive airway pressure (CPAP). The CPAP device prevents the airway from closing during sleep. A CPAP device is the most common treatment for sleep apnea. If enlarged tissues are causing the blockage, surgery may be needed.
BIPAP
Bilevel therapy works by delivering two different levels of positive air pressure: a higher level of pressure during inhalation and a lower level of pressure during exhalation. There are a number of conditions for which a physician might prescribe Bipap therapy. Bipap devices provide therapy for people with obstructive sleep apnea (OSA) if they have found CPAP therapy too difficult. Bilevel devices can also provide noninvasive position pressure ventilation (NPPV) for people with respiratory disorders of other forms of sleep-disordered breath (SDB).
The breathing device includes a compressor that delivers air, oxygen or a mixture thereof at a controlled rate to a mask that seals tightly against the patient airway. There are both nasal masks and full face masks available. CPAP manufacturers includes Devilbiss, Fisher & Paykel, Puritan-Bennett, Resmed, Respironics, Med Ind American, Inc. and Viasys. An important feature of the CPAP mask is comfort and sealing characteristics. The patient has to wear the mask at night during his sleep. During sleep the compressor delivers controlled gas pressure to the mask. Because of the pressure of the gas between the face and the mask, a relatively large force is required to keep the mask in place. This retaining force is exerted by the mask “head gear,” this is a structure of straps that holds the mask in place. The head gear pushes the mask tightly against the patient's face. Accordingly issues arise relating to comfort and skin adhesion and damage.
Some CPAP masks already commercially available have a seal made of soft elastomers, some have a double structure of an elastomer plus an additional thin film over the elastomer in order to minimize skin breakdown. The surface characteristics of the seal are important. The seal should not grab the skin at all. It should not exert tangential stresses on the skin. The patient is likely to move in his sleep and, therefore, the mask is likely to impinge on the bedding and be subject to lateral stresses. Such stress, if transmitted to the skin, will likely cause skin damage.